The present invention relates to a new and improved construction of an electrical resistance-roll seam welding machine, sometimes also referred to in the art as a resistance roll-welding machine or apparatus.
The resistance roll-welding machine of the invention is of the type comprising a pair of welding rolls and at least one electrode wire which is guided from a supply station or location for fresh wire by means of at least one of the welding rolls to a collecting station or location for consumed wire and the electrode wire can be brought into contact with the workpieces to be welded by means of the welding rolls. The welding machine further contemplates providing for the electrode wire a brake device between the supply station and the welding rolls and a tension or traction device between the welding rolls and the collecting station, the sum of the tension force exerted by means of the tension device upon the wire and the brake force exerted by means of the brake device upon the wire is large enough in order to continuously maintain in a tensioned state the electrode wire along its path of travel between the brake device and the tension device.
With state-of-the-art welding machines of the previously mentioned type the electrode wire is solely placed into movement by means of the tension device, and the wire also must drive the welding rolls and the workpieces passing between the welding rolls during the welding operation. As a result, the electrode wire is exposed to a relatively high tensional stress over its entire length between the brake device and the tension device, which can lead to appreciable elongation of the wire. This in turn can result in difficulties with respect to the synchronization of the wire drive i.e., the welding roll drive and the transport device for bringing the workpieces to be welded to the welding rolls. Hence, it is for these reasons that prior art resistance roll-welding machines of the previously mentioned type possess special means and measures in order to eliminate any deleterious effects of the momentarily arising lengthwise elongation of the electrode wire following termination of each welding operation by freely retightening the wire.